Intel Larrabee instruction set is ready-to-use

Intel just released a C++ header which allows developers to use Larrabee instructions with current compilers, by simply writing out the future instrisincs as C code. Some interesting bits:

  • 512 bit vector types (8x64bit double, 16x32bit float, or 16x32bit integer)
  • Lots of 3-operand instructions, like a=a*b+c
  • Most combinations of +,-,*,/ are provided, that is, you can choose between a*b-c, c-a*b and so forth.
  • Some instructions have built-in constants: 1-a*b
  • Many instructions take a predicate mask, which allows to selectively work on just a part of the 16-wide vector primitive types
  • 32bit integer multiplications which return the lower 32bit of the result
  • Lots of trigonometric functions [Update] They don’t say which ones map directly to instructions, and provide them only for the sake of completeness.
  • Bit helper functions (scan for bit, etc.)
  • Explicit cache control functions (load a line, evict a line — that would have been helpful on a project I worked on once)
  • Horizontal reduce functions: Add all elements inside a vector, multiply all, get the minimum, and logical reduction (or, and, etc.).

Especially the reduce functions look interesting, as they are more general than the dot-product instruction available in SSE. Nothing revolutionary though, but all in all it looks like a very nice and useful instruction set, although I was hoping for 8-bit instructions as well (with 8 bit components, and RGBA, you could process 4x4 pixels at once — that would be a real killer for image processing).

[Update] The instructions are 3 operand only, storing the result in the first operand!


Comments powered by Disqus